Download Classification of Cataract

2003
Classification of Cataract
Dr Simon Barnard
BSc PhD FCOptom FAAO DCLP DipClinOptom
Table of Contents
Table of Contents.................................................................................................. 1
Defintition .............................................................................................................. 2
Classifications ....................................................................................................... 2
Morphological classification ............................................................................... 2
Capsular ........................................................................................................ 2
Subcapsular ................................................................................................... 3
Anterior subcapsular ...................................................................................... 3
Nuclear .......................................................................................................... 3
Cortical .......................................................................................................... 3
Lamellar ......................................................................................................... 3
Sutural ........................................................................................................... 4
Aetiological classification ................................................................................... 4
Congenital cataract ........................................................................................ 4
Degenerative or Age Related (senile) ............................................................ 5
Traumatic ....................................................................................................... 5
Secondary...................................................................................................... 5
Toxic .............................................................................................................. 7
Other definitions ................................................................................................ 7
Immature or incomplete ................................................................................. 7
Mature ........................................................................................................... 7
Intumescent ................................................................................................... 7
Hypermature .................................................................................................. 7
Morganian cataract ........................................................................................ 7
Further Reading, References & Acknowledgements ............................................ 7
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Defintition
A cataract usually is defined as an opacification of the lens or its capsule
In this sense, almost every adult has cataract
Classifications
Cataract is often categorised using morphological and/or aetiological
classifications e.g., age related posterior subcapsular.
Morphological classification
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Capsular
Subcapsular
Nuclear
Cortical
Lamellar
Sutural
Cortical
Nuclear
Subcapsular
Capsular
Congenital capsular thickening
Congenital capsular thickening may be associated with posterior or anterior polar
cataracts and pyramidal cataract. The posterior form may be associated with a
hylaoid remnant.
Acquired capsular opacities
Acquired capsular opacities can occur with pseudoexfoliation, Infra-red radiation
(Glass blower’s cataract) or Secondary to blunt trauma when a Vossius’ ring may
be formed.
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Subcapsular
Posterior subcapsular
Posterior subcapsular ens changes may associated with secondary or
complicated cataracts, drugs e.g., steroids, or be an age related cataract
(Cupuliform).
Anterior subcapsular
Anterior subcapsular lens changes may be associated with
Wilson’s disease (sunflower cataract) or with drugs e.g., amiodarone
Nuclear
Congenital
An example of a congenital nuclear cataract is that secondary to Rubella
Age related
Nuclear sclerosis cataract commonly seen in practice is the age related form.
Cortical
Congenital
Congenital cortical cataract is very common and they rarely interfere with vision.
Examples include e.g., blue dot cataract and coronary cataract.
Age related
Age related cortical cataract is also known as cuneiform cataract that takes the
form of “water” clefts and vacuoles. These often appear first in the inferior nasal
quadrant of the lens possibly because this is most exposed to UV radiation.
Lamellar
Congenital
Lamellar cataracts are usually congenital and often involve one lamella of the
foetal or nuclear zones. Radial, spoke-like opacities (or riders) also often
surround the cataract.
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Sutural
These are often known as “Y”-shaped” cataract.
Of course, more ore than one type of cataract can be present in an eye.
Aetiological classification
A further way of classifying cataract is by cause.
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Congenital
Degenerative or “age related” (senile)
Traumatic
Secondary to other conditions (including metabolic causes)
Toxic
Hereditary
Congenital cataract
Congenital cataract can be a result of heredity (often autosomal dominant), prenatal infections such as rubella or metabolic disorders.
Intrauterine infections
Examples include rubella and toxoplasmosis.
Maternal drug ingestion
Examples include thalidomide and corticosteroids.
Genetically transmitted syndromes
Microphthalmos is often associated with cataract.
Ocular conditions with associated anomalies
Examples include retinopathy of prematurity and some types of retinitis
pigmentosa.
Secondary to metabolic disorders
Galactosemia and Wilson’s disease are two examples.
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In 50% of cases the cause is unknown (Dhillon & Fleck, 1996).
Degenerative or Age Related (senile)
Most adults have some degree of opacification of the lens and therefore
technically exhibit cataract.
Subcapsular
Anterior subcapsular cataract (directly under the capsule) is
associated with fibrous metaplasia of anterior lens epithelium.
Posterior subcapsular cataract (cupuliform) lies just in front of posterior capsule
and is associated with posterior migration of epithelial cells.
Cortical
Cortical cataract commonly develops as radial or spoke shaped “water-clefts”
(cuneiform) togther with vacuoles. Cuneiform changes affect anterior, posterior
and equatorial cortex affected
Nuclear sclerosis
Nuclear cataract is an exacerbation of the normal ageing of lens nucleus and
appears as a yellowing of the nucleus.
Traumatic
Trauma is the commonest cause of unilateral cataract in young individuals
((Kanski, 1992).
Opacities can be the result of various injuries including penetrating injury.
Concussion to the eye may cause the iris to be flattened against the lens leaving
a Vossius’ ring.
Secondary
Cataract can occur secondary to systemic disease or syndromes including
metabolic disorders and due to local disease (ocular).
Secondary to systemic conditions
Many conditions can cause or be associated with cataract
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Diabetes
Diabetes mellitus can cause an exacerbation of the progression of age related
degenerative changes.
So-called (classical) diabetic cataract occurs during an acute and untreated
hyperglycaemic episode and takes the form of cortical “snowflakes”. These occur
due to osmotic over-hydration of the lens and can be anterior and/or posterior in
position.
Galactosaemia
This metabolic disease produces an “oil droplet” cataract.
Wilson’s disease (hepatolenticular degeneration)
This is an anomaly of copper metabolism and produces a ring of copper in the
peripheral cornea (Kayser-Fleischer ring) and a greenish coloured “sunflower
cataract”
Atopic dermatitis
Cataract can occur secondary to atopic dermatitis and takes the form of bilateral
posterior or anterior stellate opacities.
Down’s syndrome
15% of Down’s have lens opacities severe enough to cause a decrease in acuity
(Kanski, 1998) and with a reported prevalence of up to 50% (Scully, 1973).
Secondary to local disease (or complicated cataract)
Anterior uveitis
Anterior uveitis can produce a posterior polar polychromatic cataract. Also,
if uveitis not controlled, anterior and posterior subcapsular opacities can progress
to complete opacification.
High myopia
Hight myopia can be associated with secondary posterior lens opacities as well
as earlier development of nuclear sclerosis.
Glaukomflecken
These are grey-white anterior capsular or subcapsular opacities in pupillary zone
pathonomonic with previous attacks of acute angle-closure glaucoma.
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Toxic
Many drugs can cause cataract.
Corticosteroids
Steroids used for prolonged therapy produce a posterior subcapsular cataract.
Amiodarone
Amiodarone can cause anterior capsular changes in up to 50% of patients. The
opacities tend to be visually insignificant.
Other definitions
Immature or incomplete
The cataract is present but not visually incapacitating. Surgery may or may not
be indicated.
Mature
The whole lens is opaque. Surgery is usually indicated.
Intumescent
The lens is swollen. Surgery is indicated.
Hypermature
The lens is shrunken, yellow and the capsule is wrinkled.
Morganian cataract
A hypermature cataract with liquified cortex and in which the nucleus settles
inferiorly.
Further Reading, References & Acknowledgements
Cassidy L (2001) Paediatric cataract, Optometry Today. 9th March
Dhillon B & Fleck B (1996) Diseases of the Eye and Orbit. Chhapter 12 In:
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Paediatric Eye Care, Eds. Barnard S & Edgar D, Blackwell Science,
Oxford.
Kanski J (1992) Clinical Ophthalmology, Butterworth Heinemann, Oxford
Scully C (1973) Downs’ Syndome, Brit J Hosp Med, 10, 89 and 98.
Taylor D (1990) Paediatric Ophthalmology, Blackwell Science, Oxford